1. Field of the Invention
The present invention relates to the field of fluid flow valves, and more particularly but not by way of limitation, to an improved modulating flow control valve for proportioning the flow of fluids in response to motor controls.
2. Discussion
In the control of fuel to industrial furnaces, boilers and the like, there is a need to maintain proper flow of the fuel over widely varying firing conditions. A number of prior art devices are known for varying inlet fuel valving and inlet air venting in response to monitored signals, such as temperature and stoichiometric parameters. For example, monitors are used to determine the free oxygen content of a stack gas and to trim the inlet air as the monitored reading varies from a set point.
As pointed out in numerous prior art publications, and as is known by persons of ordinary skill in this field, an industrial burner application will have variables which take each such installation beyond the range of prediction, thus requiring that each installation be provided the capability of tailoring its characterizing controls to its peculiarities over the range of its firing usage. Several prior art characterizing or proportioning control teachings are provided in the following prior art teachings.
Maxon, U.S. Pat. No. 2,286,173, teaches a valve to proportion air and fuel to industrial burner systems in which an air gate is journaled in an air passage bore and is rotatable by a segmetal arm structure. A spring loaded stemmed valve (biased closed) is supported in a fuel inlet bore. A push rod is supported to engage the stemmed valve and is operable to open same as it is pressed against the stemmed valve. Actuating means is disposed to actuate the push rod by the arm structure which supports a series of individually adjustable threaded pins carried by the arm structure to variably depress the push rod along the arc of the arm structure to vary the air-fuel ratio. A flexible strip is disposed between the push rod and the threaded pins to facilitate engagement therewith.
Voorheis, U.S. Pat. No. 2,315,171 teaches an adjustable valve in which a series of adjusting screws provide a path to selectively depress a roller supported by an operating handle connected to a valve rod which is spring biased. Thus the object of the invention, to move the valve control element through a predetermined sequence of valve settings, is achieved.
Condon et al, U.S. Pat. No. 3,706,438, teaches an operating mechanism for controlling movement of a valve element. A continuous deformable channel has a pair of opposed cam surfaces supported by adjusting screw and a support member. A follower is connected to a shaft which moves a valve element between open and closed positions. Spotz, U.S. Pat. No. 1,525,052, teaches an adjustable cam surface and a cam follower. The shape of the cam surface is determined by a plurality of adjustable struts which connect it to a carrying frame. Tritle, U.S. Pat. No. 2,323,737, teaches a control system having a cam that is mounted for pivoting on a pin and which sections may be adjusted by means of screws.
Valves for fuel oil flow are numerous in design, and more specifically, the above mentioned prior art teachings show some of these modulating flow control devices. Variable flow in a valve body can be achieved by tapered valve members, such as taught in the patents issued to: Friedmann, U.S. Pat. No. 665,083; Huff, U.S. Pat. No. 1,619,937; Bladon, U.S. Pat. No. 733,693; Pinnell, U.S. Pat. No. 3,187,775; Wood, U.S. Pat. No. 4,568,499; Gawer et al, U.S. Pat. No. 4,542,766; and Erickson, U.S. Pat. No. 1,055,152. While not exhaustive, this list provides illustrative art of various approaches to variable flow control.
None of these prior art control devices provide the advantages and the novel structure of the present invention as described herein.